Rdar 29016063 precompile bridging header

docs/Lexicon.rst

@@ -231,6 +231,17 @@ source code, tests, and commit messages. See also the `LLVM lexicon`_.
     library on the system when the library on the system cannot be modified.
     Apple has a number of overlays for its own SDKs in stdlib/public/SDK/.
 
+  PCH
+    Precompiled header, a type of file ending in .pch. A precompiled header is
+    like a precompiled module, in the sense that it's the same file format and
+    is just a cache file produced by clang and read by ``clang::ASTReader``. The
+    difference is that PCH files are not "modular": they do not correspond to a
+    named module, and cannot be read in any order or imported by module-name;
+    rather they must be the first file parsed by the compiler. PCHs are used
+    only to accelerate the process of reading C/C++/Objective-C headers, such as
+    the bridging headers read in by the ``-import-objc-header`` command-line
+    flag to swiftc.
+
   PR
     1. "Problem Report": An issue reported in `LLVM's bug tracker`__.
        See also `SR`.

include/swift/AST/DiagnosticsClangImporter.def

@@ -53,6 +53,9 @@ ERROR(bridging_header_error,Fatal,
 WARNING(could_not_rewrite_bridging_header,none,
   "failed to serialize bridging header; "
   "target may not be debuggable outside of its original project", ())
+ERROR(bridging_header_pch_error,Fatal,
+   "failed to emit precompiled header '%0' for bridging header '%1'",
+   (StringRef, StringRef))
 
 WARNING(invalid_swift_name_method,none,
   "too %select{few|many}0 parameters in swift_name attribute (expected %1; "
@@ -76,6 +79,11 @@ WARNING(unresolvable_clang_decl,none,
         "imported declaration '%0' could not be mapped to '%1'",
         (StringRef, StringRef))
 
+WARNING(implicit_bridging_header_imported_from_module,none,
+        "implicit import of bridging header '%0' via module %1 "
+        "is deprecated and will be removed in a later version of Swift",
+        (StringRef, Identifier))
+
 #ifndef DIAG_NO_UNDEF
 # if defined(DIAG)
 #  undef DIAG

include/swift/ClangImporter/ClangImporter.h

@@ -201,13 +201,16 @@ class ClangImporter final : public ClangModuleLoader {
   /// \param diagLoc A location to attach any diagnostics to if import fails.
   /// \param trackParsedSymbols If true, tracks decls and macros that were
   ///        parsed from the bridging header.
+  /// \param implicitImport If true, indicates that this import was implicit
+  ///        from a reference in a module file (deprecated behaviour).
   ///
   /// \returns true if there was an error importing the header.
   ///
   /// \sa getImportedHeaderModule
   bool importBridgingHeader(StringRef header, ModuleDecl *adapter,
                             SourceLoc diagLoc = {},
-                            bool trackParsedSymbols = false);
+                            bool trackParsedSymbols = false,
+                            bool implicitImport = false);
 
   /// Returns the module that contains imports and declarations from all loaded
   /// Objective-C header files.
@@ -218,6 +221,14 @@ class ClangImporter final : public ClangModuleLoader {
   std::string getBridgingHeaderContents(StringRef headerPath, off_t &fileSize,
                                         time_t &fileModTime);
 
+  /// Makes a temporary replica of the ClangImporter's CompilerInstance, reads
+  /// an Objective-C header file into the replica and emits a PCH file of its
+  /// content. Delegates to clang for everything except construction of the
+  /// replica.
+  ///
+  /// \sa clang::GeneratePCHAction
+  bool emitBridgingPCH(StringRef headerPath, StringRef outputPCHPath);
+
   const clang::Module *getClangOwningModule(ClangNode Node) const;
   bool hasTypedef(const clang::Decl *typeDecl) const;
 

include/swift/ClangImporter/ClangImporterOptions.h

@@ -35,6 +35,9 @@ class ClangImporterOptions {
   /// Equivalent to Clang's -mcpu=.
   std::string TargetCPU;
 
+  // The bridging header or PCH that will be imported.
+  std::string BridgingHeader;
+
   /// \see Mode
   enum class Modes {
     /// Set up Clang for importing modules into Swift and generating IR from

include/swift/Driver/Action.h

@@ -48,9 +48,10 @@ class Action {
     REPLJob,
     LinkJob,
     GenerateDSYMJob,
+    GeneratePCHJob,
 
     JobFirst=CompileJob,
-    JobLast=GenerateDSYMJob
+    JobLast=GeneratePCHJob
   };
 
   static const char *getClassName(ActionClass AC);
@@ -268,6 +269,17 @@ class GenerateDSYMJobAction : public JobAction {
   }
 };
 
+class GeneratePCHJobAction : public JobAction {
+  virtual void anchor();
+public:
+  explicit GeneratePCHJobAction(Action *Input)
+    : JobAction(Action::GeneratePCHJob, Input, types::TY_PCH) {}
+
+  static bool classof(const Action *A) {
+    return A->getKind() == Action::GeneratePCHJob;
+  }
+};
+
 class LinkJobAction : public JobAction {
   virtual void anchor();
   LinkKind Kind;

include/swift/Driver/ToolChain.h

@@ -122,6 +122,9 @@ class ToolChain {
   constructInvocation(const GenerateDSYMJobAction &job,
                       const JobContext &context) const;
   virtual InvocationInfo
+  constructInvocation(const GeneratePCHJobAction &job,
+                      const JobContext &context) const;
+  virtual InvocationInfo
   constructInvocation(const AutolinkExtractJobAction &job,
                       const JobContext &context) const;
   virtual InvocationInfo

include/swift/Driver/Types.def

@@ -60,6 +60,7 @@ TYPE("remap",           Remapping,          "remap",           "")
 
 // Misc types
 TYPE("pcm",             ClangModuleFile,    "pcm",             "")
+TYPE("pch",             PCH,                "pch",             "")
 TYPE("none",            Nothing,            "",                "")
 
 #undef TYPE

include/swift/Frontend/FrontendOptions.h

@@ -149,6 +149,8 @@ class FrontendOptions {
     /// Parse, type-check, and dump type refinement context hierarchy
     DumpTypeRefinementContexts,
 
+    EmitPCH, ///< Emit PCH of imported bridging header
+
     EmitSILGen, ///< Emit raw SIL
     EmitSIL, ///< Emit canonical SIL
 

include/swift/Option/FrontendOptions.td

@@ -235,6 +235,9 @@ def disable_modules_validate_system_headers : Flag<["-"], "disable-modules-valid
 def emit_verbose_sil : Flag<["-"], "emit-verbose-sil">,
   HelpText<"Emit locations during SIL emission">;
 
+def emit_pch : Flag<["-"], "emit-pch">,
+  HelpText<"Emit PCH for imported Objective-C header file">, ModeOpt;
+
 def enable_sil_ownership : Flag<["-"], "enable-sil-ownership">,
   HelpText<"Enable the SIL Ownership Model">;
 

include/swift/Option/Options.td

@@ -237,6 +237,14 @@ def disable_swift_bridge_attr : Flag<["-"], "disable-swift-bridge-attr">,
   Flags<[FrontendOption, HelpHidden]>,
   HelpText<"Disable using the swift bridge attribute">;
 
+def enable_bridging_pch : Flag<["-"], "enable-bridging-pch">,
+  Flags<[HelpHidden]>,
+  HelpText<"Enable automatic generation of bridging PCH files">;
+
+def disable_bridging_pch : Flag<["-"], "disable-bridging-pch">,
+  Flags<[HelpHidden]>,
+  HelpText<"Disable automatic generation of bridging PCH files">;
+
 // Diagnostic control options
 def suppress_warnings : Flag<["-"], "suppress-warnings">,
   Flags<[FrontendOption]>,

include/swift/Strings.h

@@ -18,6 +18,8 @@ namespace swift {
   static const char SERIALIZED_MODULE_EXTENSION[] = "swiftmodule";
   /// The extension for serialized documentation comments.
   static const char SERIALIZED_MODULE_DOC_EXTENSION[] = "swiftdoc";
+  /// The extension for PCH files.
+  static const char PCH_EXTENSION[] = "pch";
   /// The extension for SIL files.
   static const char SIL_EXTENSION[] = "sil";
   /// The extension for SIB files.